I'm currently studying in the computer science field and I came across some interesting topics concerning data transmission and coding theory. This may not concern the search for signals directly, but the ability to possibly decode or interpret them if they do exist. If I recall correctly, Mr. Seth Shostak (or perhaps somebody else) advocated the benefits of searching for signals in a talk, which included the possibility of listening to signals that encompass technologies that are more advanced than ours (and thus very valuable). But this question would also concern much simpler transmitted information, such as a sequence of numbers or other encoded data.

So as I read about communication with far away satellites and other exploring spacecraft that are in interplanetary space (f.e. mars orbiters, juno spacecraft, voyager, etc.) there are two things that grabbed my attention. First, due to cosmic radiation, radio signals seem likely to get corrupted while traveling through space. Second, if a corrupted data package (such as a photo encoded in binary) is received on earth, it is impractical to send a message back and ask the sender to send the packet again due to the time it takes (even though it travels with the speed of light). Therefore the need for error-correcting code (as part of the coding theory).

Perhaps my assumption is wrong, but if other intelligent life exists and has developed the technology to transmit radio signals, they may also have some kind of computer science theory as part of mathematics (which to me seems pretty universal). So the idea of bits (1 and 0, on and off, true and false, ...) may not be far fetched. And if they also send their data in binary, cosmic radiation might turn a zero into a one and the other way around. So no matter if they just send out the fibonacci series or broadcast images or music in binary, it probably wouldn't even make it out of their solar system without being corrupted.

If we do find a signal, I bet a lot of time and effort will be spent on trying to decipher or make sense of it in some way. But is this even possible? If they do package the information in some error-correcting code, how could we decode it without knowing what they used to encode it? If we were to broadcast anything, how will other lifeforms be able to decipher our error-correcting code? If a "nearby" advanced civilization notices us and we notice them, and want to communicate via radio, how could we agree on a common protocol and encoding scheme if the instructions for decoding would become corrupted in transit as well?

Or perhaps I misunderstood something along the way. Either way, I found this topic highly interesting and I thought this could be the right place to get some thoughts from you guys. What do you think? What types of signals are we expecting? How much does cosmic radiation affect possible signals? Of course I would be very satisfied with any signal at all, but actual interstellar communication would be a cherry on top.

Two issues with inter-stellar communication
First, dispersion. Over the distances involved radio waves will be scattered, and thus be less readable when they get to the far end of the communications link. Digital communications can go some way to overcoming this.
Second, time lag. Our nearest star is 3 light years away, radio waves travel at the speed of light, so any dialogue would have a six year delay between initiation and receipt of acknowledgment. Not exactly conducive to ready conversation. Digital technologies don't help here.Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

Repetition codes, though very inefficient, have the advantage of simplicity. If each block of data is sent repeatedly, a consistent number of times, this scheme will soon make itself obvious.

Random or sporadic flipping of a binary digit by noise would be unlikely to corrupt most data blocks, or to corrupt the same digit in most blocks. The predominant version of the data block, among the repetitions , could be assumed to be the correct one.
Such a message could contain instructions on the use of a more complex and more efficient method of error correction, establishing a standard technique for a particular communications channel.

Repetition codes, though very inefficient, have the advantage of simplicity. If each block of data is sent repeatedly, a consistent number of times, this scheme will soon make itself obvious.

Thank you! I didn't even think about the option of just sending the same block of data lots of times. Since the possibility of corruption is already a problem for interplanetary communication, I thought the radiation beyond our solar system would be an even bigger problem and thus making "raw" data without error-correction generally implausible. But as you said, even though there is a chance the same binary digits flip in sent blocks it decreases with an increase in the amount of repetitions.

Such a message could contain instructions on the use of a more complex and more efficient method of error correction, establishing a standard technique for a particular communications channel.

The missing agreed upon communication protocol was what worried me the most. Even though I suspect it would not be very easy to find a way to formulate the instructions in a way that some other lifeform can interpret it correctly, with enough time and dedication on both sides this could lead to actual corresponence. Your answer was very helpful, thanks!

First, dispersion. Over the distances involved radio waves will be scattered, and thus be less readable when they get to the far end of the communications link. Digital communications can go some way to overcoming this.

Agreed, I would think that a bit is less likely to be flipped or wrongly interpreted when the signal weakens. But if we knew where exactly our communication partner is, wouldn't we be able to focus the waves better? Although that might depend on how far away the other solar system is.

Second, time lag. Our nearest star is 3 light years away, radio waves travel at the speed of light, so any dialogue would have a six year delay between initiation and receipt of acknowledgment. Not exactly conducive to ready conversation. Digital technologies don't help here.

Exactly, these long transmission times are why the error-correcting codes are so important. We couldn't just ask for a new version of the data because the one we received is corrupted. Personally I think that even though it might take a long time, a conversation would still a great goal. At the beginning it would probably be very simplistic because there is no common language, maybe some numbers or relations. Then some instructions on how to decipher more complicated information. It might take many generations, but I think it would be worth it simply because that would be a great achievement for a lifeform such as ourselves. Also, without some sort of faster than or close to light travel, that might be the only way to interact with them.

William's right. It is far easier to just detect a signal from an intelligent source, than to worry about what it says.
Suppose aliens about 50 light years out are just detecting I Love Lucy.
Most likely all they would recognize is a signal coming from somewhere near our sun that was not natural.

Math expert, I'm not, by far, but I think it might not be too difficult to indicate a simple form of error correction. Let's try an experiment.
What would you make of the following sequence, sent repeatedly? Dashes inserted merely to indicate a timing space.

The left column is counting by 2's in Binary. The right column makes no sense. Aliens schooled in Base two arithmetic would dismiss the sequence until they saw that it was repeated then they would scratch their heads and probably conclude that there was no useful information encoded. They might conclude that this was a purposive beacon and might scan this section of their sky to see what they might see or hear.

Left column is a simple binary count in the three leftmost bits with the least significant bit not used (or just counting by twos), the right column is an odd parity bit.“Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it's the only thing that ever has.”---Margaret Mead

Quite correct! Since this was so readily perceived, perhaps it would be perceivable, too, by mathematically minded extraterrestrials. Would anyone care to devise a comparable cluing method for the use of a check sum?

Interesting little experiment, I read your answer just now but I agree with the others on the interpretation. I found this youtube video that explains the problem and solution using error correcting codes really well:https://www.youtube.com/watch?v=NRv3HMEyuDE

Parity checking and other methods (such as a checksum) work well to find out that there are errors, but to actually be able to correct flipped bits we would probably need more extensive codes. In the video, the professor talks about simply sending a greyscale picture of mars, which basically means sending a numbers between 0 and 63 back to earth (color of a pixel). The coding experts thought there would be up to 25% (!) corruption or flipped bits, which means they needed to send 32-bit messages for just 6 bits of information (2^6 = 64) with a distance of 16 (-> 7 bits can be corrected, as he calculates in the video). There is a part 2 of this video, and he explains that you can scale this, f.e. sending 64-bit messages with even more error correcting possibilities. But the longer you make a message, the more likely it is that it gets corrupted at all.

Now what concerned me here was that they calculate with 25% corruption just between mars and earth (depending on how far apart they are at any given time). Now think about how much corruption you would have to think about on a mission to pluto or even outside our solar system. I'm not very advanced in astrophysiks but as far as I know there is a lot of cosmic radiation beyond the limits of our solar system. If we would need to correct 75% or more errors, the error-correcting codes would need to be massive. But I'm not sure how much of an effect the radiation actually has on radio signals, which is also one of the reasons I opened this thread.

Sure, they may not be digital. But as far as I know it is easier to send a 0 or a 1 using radiowaves than lets say 0, 1, 2, and 3.

@SciManStev

It is far easier to just detect a signal from an intelligent source, than to worry about what it says.

Sure, I would be very happy to just detect a signal that is not from a natural source. My question was more hypothetical and discusses what we could do after we actually get a signal from a nearby star (or they found our I love lucy signals and are trying to communicate with us).

We have not heard an eavesdropping style of alien signal now for 50 years and we are not likely to find one in the future.

Now: for high powered purposive "we are here" types of signals we would not expect them to be encrypted nor using any type of error correcting code.

Here is what we would (should) do if we found a strong signal of apparent non-Earth origin:

Hopefully we will have recorded the damn thing and it's position in the sky--it may be a one time blast from a slewing beacon.
Use auto-correlation techniques to raise the signal up out of the noise. Guess at the pulse form (square wave ?) to enhance this
Look for a modulation scheme and message type: Am, FM, Side band, ON-OFF
Demodulate to look for: --video raster, picture, audio, counting out numbers.
look for repetition within the message.
Look for a primer either of language or number representation

I posted the previous at 6:30 AM this morning even before the cup of coffee.

But I read the news about a possible thought around about possibly widening our search.

One possible way of perhaps believing in other intelligent civilizations in space is that of making observations of UFO's in the sky and next make such an assumption.

Another way could be that of looking at the Drake equation and making an assumption, or possible guess about any such civilizations.

A third way could be that of signal analysis and processing by the Seti@home client, in the hope that possible numbers being returned could tell about such a fact.

Still, the fact that some of us happen to be scientists, or even UFO researchers at times, while others could be either biologists, anthropologists, or possibly even
mathematicians or physicists as well.

If you for some reason are unable to "believe", you could end up being either a debunker or maybe a skeptic.

There could be a third description for this as well, but looking through, I am unable to find this word.

The Wikipedia chooses to make two separate articles for that of nature and that of science.

If God chose to give us those numbers to be dealing with, we would next assume that a Creation as such, or by means of its word would be of a given meaning and therefore
could be of an intended such meaning.

Eminent scientists like Stephen Hawking, Michio Kaku and Steven Weinberg has brought us back to the first minutes or less after the initial Creation of the Universe.

A given understanding of such a Creation by means of science apparently is only possible by means of that of Matter Creation for such a thing.

Again, notice the use of large caps here for a couple of words, because of my inclination, or perhaps belief that the laws of nature did not come into existence on its own,
because of the fact that both perfect symmetry and that of random chaos could both be explained by mathematical laws and equations and also that chaos is the usual thing around.

Such a thing as "Intelligent Design", by means of subject, could be that of construction of cars, roads, bridges and high-rised buildings.

The smile of Mona Lisa becomes something completely different and we all know that.

For a given painting we also should be having a painter for such a thing, in the same way as music is having a composer for its origin.

For such a thing as the Universe, that of Matter Creation is still our only way of dealing with the origin of its creation, because assuming the Big Bang as its moment of creation,
both matter and energy came into existence, together with the force of gravity.

If we for some reason could believe in such a thing as both "Little Green Men" and other intelligent civilizations in space, we still would have to rely on the basic conditions which makes this possible.

By means of both Laws and Equations for a couple of things, we could next assume that certain conditions, or "constraints" makes for one given possibility, but perhaps not another.

The speed of light in vacuum, or empty space, is some 300,000 km/s.

A hypothetical particle called the Tachyon could be always moving faster than the speed of light if it exists.

If you could be left to choose between such a thing as prime numbers, or factors, including the so-called "RSA numbers", or that of the UFO phenomenon in order to make up your possible mind,
chances are that you could be left 50/50 for such a thing.

If for some reason that of the Uncertainty Principle could belong to that of Electromagnetism as being one of the Fundamental Forces of Nature, this could next mean that both Special and General Theory of
Relativity could be part of a similar scheme, meaning that of such Fundamental Forces of Nature.

But apparently not so.

There definitely could be some people being of the opinion that ball lightning is not the same as a UFO observation.

Such a thing as creativity may not be the same as that of Creation for its meaning.

Therefore such a thing as "Collective Evolution" being used on my Facebook page (needs checking), may not necessarily be the same as neither design, intelligence, or even conscience either.

Everyone knows that it is impossible to count the number of grains of sand on a beach.

Still we could be doing such a thing with both numbers and also the elementary particles of nature by means of quantisizing their possible function or meaning, or perhaps purpose.

Making a car by means of both construction and design for such a thing is not the same as a painting like Mona Lisa, but for both we could be having an assumption that such a creativity
could mean the same as a possible conscience in nature itself.

For such a thing it is rather more easy to deal with the subject of Religion and Faith for such a thing.

Nature could be both "Heaven and Hell" by means of its Creation, but such a thing is not always evident or visible by means of that of Matter Creation.

If such a thing as Philosophy could be better at giving an answer to the questions being asked, we next would have to know what Philosophy is all about.

The Greek scientists were more or less Philosophers in such a way, but they were only able to come up with that of earth, wind, soil and fire for the most basic ingredients.

I think that the fact that should be quite well known is the fact that "believers" find it quite hard to explain the concept or notion of the possible divine to that of scientists.

It becomes two different worlds and for now we apparently are unable to agree on a common issue related to to this subject.

Unfortunately I do not have the details, but we could be left to believe that Stephen Hawking could be able to either make a conclusion about this subject, or possibly reject it altogether,
only because of his sharp mind.

If science alone could be able to make such a conclusion, I would of course be happy to know the reason for this.

Communication implies that the two ends of the link "talk" to each other. This is irrespective of what the modulation and encoding of the message. We are used to "talking" in near real time, not with a many year delay between calling our presence and getting the response, this makes communication, as opposed to broadcast, which is when the sender just shouts into the ether", and does not expect (or require) any response from any receiver of the message.Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

I think we humans not only will communicate but also explore the universe beyond interstellar space.
The means of doing that is quantum communication, i.e through entanglement, and sending small robotic spacecrafts. Probably also Van Neumann probes for planetary research whose information can be relayed home by quantum satellites.
That will give us the tools of observing and collecting knowledge in near real time regardless of distances long before we can travel ourself.

Interstellar is the matter that exists in the space between the star systems in a galaxy, beyond that is intergalactic space between galaxies. The nearest star in our own Milky Way galaxy is Alpha Centauri 4.4 light years from earth. To explore even the nearest star would take space probe 4 years to get there at light speed.

The recently discovered Canis Major dwarf galaxy, is 25,000 light-years away, and the Andromeda full size galaxy is 2.5 million light years away. So unless we can break the speed of light barrier we ain't going to be sending probes to other stars outside our Solar System anywhere soon. And is Einstein was right, we never will either.

How we communicate with a probe when it gets there is another matter of conjecture.